1. Field of the Invention
This invention relates to a method and apparatus for generating a parallax image string used for preparing a holographic stereogram.
2. Description of the Related Art
A parallax image string, made up of plural images having the parallax information, is used in preparing, for example, a holographic stereogram configured for displaying a stereographic image thereon. The holographic stereogram is prepared by sequentially imaging an object from different viewing points to produce a parallax image string made up of a large number of images and by sequentially recording the parallax image string as an original image on a sole recording medium for holograms as strip- or dot-shaped elementary holograms.
For example, referring to FIG. 1, in generating a holographic stereogram having the parallax information only in the transverse direction, an object 100 is sequentially imaged from different viewing points in the transverse direction to produce a parallax image string 101 made up of plural images having the parallax information only in the transverse direction. The images 102 making up the parallax image string 101 are sequentially recorded as strip-shaped elementary holograms on a recording medium for hologram 103 so that these images 102 will be consecutive to one another in the transverse direction. This produces a holographic stereogram carrying the parallax information in the transverse direction.
If this holographic stereogram is viewed from a certain position with one eye, a two-dimensional image, as an assembly of the image information of portions of the respective elementary holograms, is seen. If the eye position is moved horizontally, another two-dimensional image, as an assembly of the image information of different portions of the respective elementary holograms, is seen. Therefore, if this holographic stereogram is seen by a viewer with both eyes, the two-dimensional images, seen with left and right eyes, differ slightly from each other because of the difference in the positions of the left and right eyes. This causes the viewer to perceive the parallax so that a three-dimensional image is reproduced in the horizontal direction. This sort of the holographic stereogram is described in, for example, the Japanese Laying-Open Patent H-10-20756.
When photographing a parallax image string as an original image for the holographic stereogram, an object is imaged from different directions as an image pick-up device is moved. This generates a parallax image string made up of plural images having the parallax information. Specifically, a video camera, designed to perform image pickup at a rate of 30 frames per second, is used as an image pick-up device, and the object is imaged in succession as the video camera is moved at a preset speed. If the image is photographed for e.g., 7.5 second, 225 frames can be photographed, as a result of which a parallax image string made up of 225 images having different viewing points with respect to the object is produced.
Since a parallax image string is obtained on sequentially imaging an object, certain time is taken in imaging the parallax image string. If the object is stationary, there is raised no problem even if longer time is needed in photographing the parallax image string. However, if the object is not stationary, for example, if the object is a human being, it is desirable that the time taken in photographing the parallax image string be as short as possible, because the object is likely to move during imaging.
However, if, when the number of the frames that can be photographed in unit time is set, the time taken in imaging the parallax image string is shortened, and the number of images that make up the parallax image string is decreased. In this case, the stereoscopic image produced from the parallax image string is deteriorated in image quality.
That is, there is a relation of trade-off between the time taken in photographing the parallax image string and the quality of the stereoscopic image produced from the parallax image string, such that it has so far been difficult to maintain the sufficient image quality of the stereoscopic image derived from the parallax image string while the time taken in photographing the parallax image string is reduced.
It is therefore an object of the present invention to provide an image processing method and apparatus whereby it is possible to reduce the time needed in photographing a parallax image string and yet to render it possible to maintain the sufficient image quality of the stereoscopic image derived from the parallax image string.
In one aspect, the present invention provides an image processing apparatus for generating a parallax image string composed of a plurality of images carrying the parallax information, including image frame number adjustment means for equating the numbers of image frames making up each of a plurality of parallax image strings to one another, and image synthesis means for synthesizing the parallax image strings, the numbers of the image frames of which have been equated to one another by the image frame number adjustment means, to generate a new parallax image string.
In another aspect, the present invention provides an image processing method for generating a parallax image string composed of a plurality of images carrying the parallax information, including equating the numbers of image frames making up each of a plurality of parallax image strings to one another, and synthesizing the parallax image strings, the numbers of the image frames of which have been equated to one another, to generate a new parallax image string.
In general, in reproducing a stereoscopic image from a parallax image string, the number of original image frames necessary to maintain the image quality of the reproduced image differs with the fixing position of the reproduced image. For example, if the respective images making up a parallax image string are sequentially recorded as elementary holograms on the recording medium for holograms to produce a holographic stereogram, the number of original frames necessary to keep the same image quality differs depending on whether the reproduced image is to be localized on a place recessed from the surface of the recording medium for hologram, on the surface of the recording medium for hologram or on a place lying ahead of the surface of the recording medium for hologram. The reason is that the correlation of the images at respective viewing points differs with the localized positions of the reproduced image.
Therefore, if the object is imaged as the number of the image frames of the parallax image string is changed with different localized positions of the reproduced image, it is possible to photograph optimum numbers of image frames of the parallax image string in meeting with the localized positions of the reproduced image. Stated differently, photographing of a number in excess of the required number of the image frames is not needed to render it possible to diminish the time necessary for imaging a parallax image string. However, the plural parallax image strings, thus produced, cannot be directly used for regenerating a stereoscopic image.
Thus, according to the present invention, the numbers of the image frames making up each of plural parallax image strings are equated and the resulting parallax image strings are synthesized to generate a new parallax image string. This renders it possible to generate a parallax image string, from which to generate a stereoscopic image, from plural different parallax image strings.
Thus, according to the present invention, the numbers of the image frames making up each of plural parallax image strings are equated and the resulting parallax image strings having the equal number of image frames are synthesized to generate a new parallax image string. This renders it possible to generate a parallax image string, from which to generate a stereoscopic image, from plural different parallax image strings.
Specifically, according to the present invention, an object can be imaged as the number of image frames of the parallax image strings are changed, whereby it is possible to photograph an optimum number of image frames of the parallax image strings in meeting with the objects. That is, according to the present invention, it is unnecessary to photograph the objects more than a required number of times to render it possible to diminish the time in photographing the parallax image strings. Stated differently, it is possible to maintain the image quality of the stereoscopic image obtained from the parallax image strings as the time needed in photographing the parallax image string is reduced.